Oxygen atoms substituting sulfur atoms of MoS2 to activate the basal plane and induce the phase transition for boosting hydrogen evolution

The inertness of in-plane S atoms in MoS2 leads to unsatisfactory performance in hydrogen evolution reaction (HER). Herein, we fabricate an efficient MoS2-based catalyst (O-MoS2) with oxygen substituting a little part of sulfur in MoS2. Because the introduced O heteroatoms have the stronger electronegativity than S, the inert basal surface is activated, providing numerous active sites, improving the electrical transmission efficiency, and inducing the transition from the 2H to 1T phase of MoS2. The overpotential of as-fabricated O-MoS2 at 10 mA/cm2 is only 120 mV in alkaline electrolyte. Density functional theory calculations demonstrate that introducing O heteroatoms into MoS2 optimizes the adsorption of H∗ and decreases the Gibbs free energies of the water dissociation, thus improving the HER performance significantly. This work paves a new way to enhance the electrocatalytic activity by introducing heteroatoms with electronic modulations.